attribute vec4 a_Position ;

uniform mat4 u_Matrix;

varying vec4 v_Color;


void main(){

    gl_Position = u_Matrix * a_Position;

    float color;

    if(a_Position.z > 0.0){
       color = a_Position.z;
    }else{
       color = -a_Position.z;
    }

    v_Color=vec4(color,color,color,1.0);
}